Aerosol package providing uniform foams



Aug. 12, 1969 H. w. MACE AEROSOL PACKAGE PROVIDING UNIFORM FOAMS Filed July 24, 1967 .5m/Ewa@ Heeey Wl Mncs @uw f 44%@ United States Patent Olhce 3,460,714 Patented Aug. 12, 1969 3,460,714 AEROSOL PACKAGE PROVIDING UNIFORM FOAMS Harry W. Mace, Milford, Conn., assignor to Aerosol Techniques Incorporated, Milford, Conn., a corporation of New York Filed July 24, 1967, Ser. No. 655,509

Int. Cl. B6Sd 83/14, 79/00 U.S. Cl. 222-4 9 Claims ABSTRACT F THE DISCLOSURE An aerosol dispensing package in which a reservoir body of liqueiied propellant is provided, independent of the liquid product to be dispensed, for progressive vaporization with package use, thus eliminating the problem of depletion of propellant concentration in the dispensible product, as head space in the package increases, and resultant foam variation.

BACKGROUND OF THE INVENTION Field of the invention This invention has to do with aerosol packages. Typically such packages are comprised of a pressureresistant container provided with a finger-actuated valve dispenser. Within the container there is a pressurizing amount of a normally gaseous material termed a propellant, and a liquid product, such as a soap solution, for discharge through the valve dispenser under pressure from the propellant. A certain amount of the propellant is liquefied and dispersed throughout the liquid product under pressure of the gaseous propellant in the head space above the liquid level. The container includes a dip-tube which extends from the valve to below the liquid level for passage of the product from the container. The dispersed, liquefied propellant carried out of the pressureized container interior with the liquid product expands on reaching an atmospheric pressure zone and there results a foam or aerosoL The obtaining of a satisfactory foam obviously depends on adequate levels of propellant in the liquid product as dispensed. Too low propellant levels produce a high density, i.e. lightly foamed too wet product, known as soup in the trade. In addition to being unaesthetic, often such dense foams are ineffective for their intended purpose, e.g. as shave creams. Too low levels of foam are attributed to loss of dispersed liquefied propellant to the gaseous propellant phase in the container head space. This loss is occasioned by a progressive increase in the volume of the head space with successive discharge of the liquid product to use. The increasing head space lowers gas pressure therein and as a result additional amounts of dispersed propellant are permitted to leave the liquid product. rIlhe result is progressive deterioration of output foam.

Prior art The difficulty discussed above is recognized in the art, e.g. in U.S. Patent 2,655,480 to Spitzer. The solution in the past has been to tolerate a somewhat overfoamy dry product at the beginning so as to have marginally useful wet foam toward the end of package life. Of course, this transition means a variation in product appearance and possibly performance from first to last use, which is obviously undesirable.

It has been suggested with respect to nonfoaming products to provide a separate liquefied propellant phase in the aerosol container for the purpose of replenishing 'head space gas phase propellant. Thus in U.S. Patent 2,995,278 to Clapp, a non-aqueous layer of propellant and an underlying aqueous product layer are shown with the non-aqueous laye-r in phase equilibrium with the propellant. Provision for mixing the gaseous propellant and aqueous product on discharge was provided by means of a particular nozzle design. In U.S. Patent 2,728,495 to Eaton, a separate liquid propellant phase is disclosed, for propelling a non-foaming product. In the Eaton device the lowermost liquid propellant phase Vaporizes with product use, the vapors passing through the liquid product to the head space. Industrial and Engineering Chemistry, vol. 47, No. 6, p. 1198 et seq. (June 1955) discusses both two phase and three phase (i.e. Eaton) systems of propellant-product arrangement.

The art has not addressed itself to the problem of maintaining a foam generating amount of `propellant in a liquid product despite successive uses of the product. In packages wherein the propellant when liquefied is not soluble in the liquid product, resort must be had to an emulsion of the propellant and product. lf a liquid/ liquid emulsion or a gas/liquid emulsion, stability is a problem likely to cause Variations in output foam. In Eaton-type packages obviously no propellant is maintained in the liquid product, it passes 'by gravity, right through the product. In Clapp U.S. Patent, 2,995,278 mixing of propellant and product is mechanically accomplished on discharge from the package and may be expected to vary with the condition and care in use of the mechanism.

SUMMARY OF THE INVENTION It is one of the major objectives of the present invention to keep foaming products dispensed from aerosol packaging uniform throughout package life. This objective is achieved by retaining a constant level of propellant dispersed in the liquid product, whatever the volume of head space in the container. With the product-propellant level constant, foaming characteristics are consistent and product variations minimized. Thus, shave creams packaged in accordance with the present invention will not vary from too dry by virtue of too great foaming to soupy by virtue of too little foaming with product use.

The present invention has been occasioned by the need to improve the uniformity of foaming soap solutions such as shave cream but the principles discovered are adaptable to many liquid products as will be evident from the ensuing description, which for illustration treats specifically of soap solutions.

Another object of the present invention is to ease the criticality of charging exact amounts of propellant to a package by providing a package tolerant of fairly wide variation in propellant content.

In general, the present invention provides an aerosol dispensing package including a pressure resistant container having a dispensing means. Within the container there is provided a partially liquefied normally gaseous propellant and a liquid product having a suiicient amount of liquefied propellant dissolved therein to adequately foam on being dispensed from the package. Novelly a body of coalesced liquid propellant is also provided within the container, exteriorly of the liquid product, and in phase equilibrium with gaseous propellant in the container. The body of liqueiied propellant constitutes a means for maintaining propellant pressures within the container at product expelling levels following partial dispensing of the product, while simultaneously maintaining an adequate foaming amount of dissolved propellant in the liquid product. Provision'for the coalesced propellant body may be made by charging an amount of propellant to the container greater than that stably dispersible in the liquid product, e.g. by a margin of 0.1 to 10% of the container volume. For example, the liquid product may be saturated with propellant and the propellant body form a layer thereover and below the gas phase propellant in the head space. The liquid product typically may comprise `a solid or liquid material soluble in an hydroxylated liquid solvent such as water, alcohol or glycol and dissolved therein at appropriate concentrations and the propellant typically a low molecular weight organic compound, normally gaseous and preferably nontoxic, such as a halogenated hydrocarbon, e.g. chloroand fluorogroup substituted hydrocarbons and generally having a liquid specific gravity less than t-he liquid product. The container contents will usually be dispensible through a valve having a dip tube extending through the container to the liquid product, and through the liquefied propellant body layer normally atop the liquid product.

There is also provided by the present invention a method for maintaining propellant pressure within an aerosol package containing a propellant and a liquid product, in which the propellant is soluble, following successive partial depletions of the product level without varying the proportion of propellant dissolved in the product which includes maintaining in the package interior a coalesced body of liquefied propellant exteriorly of the liquid product and in phase equilibrium with gaseous propellant and vaporizing portions of the propellant body progressively with successive reduction in product level within the package. The body of liquefied propellant can be formed by charging to the package excess propellant to be coalesced exteriorly of the liquid product.

These and other objects and advantages of the invention, as well as the details of illustrative embodiments, will be more fully understood from the following detailed description of the drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a view in vertical section of an aerosol package according to the present invention;

FIGS. 2a, b and c are fragmentary elevational views, generally similar to FIG. 1, showing (2c) the restoration of the propellant reserve layer following dispersion of the layer material into the liquid product as a gas (2a) or a liquid (2b); and

FIG. 3 is a fragmentary view, generally similar to IFIG. 1, of a modification of the aerosol package.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, an aerosol container of pressure-resistant construction and having a sidewall 12, a bottom 14 and a domed top 16 is provided with a dispenser 18. The valve dispenser l8r includes a valve controlling communication between dip tube 22 projecting downwardly therefrom into the interior 24 of the container 10 and passage 26 through dispensing top 28 and nozzle 30. The top 28 is linger depressible by application of digital pressure on surface 32 thereof for actuation of the valve 20.

Disposed in the interior 24 of the container are three distinct layers of material occupying respectively a lower portion 34, intermediate portion 36 and upper portion 38 of the container interior. A layer of liquid product 4t? such as an aqueous soap solution is disposed in container lower portion 34 as the bottom layer. On top of the liquid product layer 40 in intermediate portion 36 of the container interior is a reservoir of propellant in t-he form of a body 42` of coalesced liquefied propellant, typically occupying from 01.1 to 10% of the container interior volume. A third layer 44` comprised of gaseous propellant is disposed in upper container portion 38 above the liquefied propellant and in phase equilibrium therewith.

Operation of the just-described aerosol package is as follows:

The dispensing top 2S is depressed by digital pressure on surface 32. This opens valve 26 to provide communication between dip tube 22 and nozzle 30 through passage 26. The lower pressure outside the container 10 relative to that within the container interior 24 exerted by the pressurizing gaseous propellant layer 44 forces liquid product 4t) up the dip tube 22 and out into the atmosphere indicated at `46. Propellant dissolved in the liquid product 40` expands rapidly on leaving the pressurized confines of the container It) and forms gas filled voids throughout the liquid product.

Thus far described, the operation of the aerosol package is conventional. In packages heretofore known the successive discharge of product, in the manner just described, operates to lower the level of liquid product 40 in the lower container portion 54 and to increase the volume of gaseous propellant `44 in the upper container portion 38. Increased volume of upper portion 38, or head space, above the liquid product 4f) requires the gaseous propellant 44 to fill the ever increasing space. This results in putting the same amount of gaseous material in a larger and larger space, which obviously lowers the pressure in that space, such pressure being proportional to the amount of gaseous material in a given volume.

The liquid product as described contains dispersed liquefied propellant. If dissolved in the liquid product, the liquefied propellant exists in the liquid product with respect to the gaseous propellant phase essentially as though the liquid product was not present. That is, the gaseous propellant pressure keeps the liquefied propellant liquefied and thus dissolved in the liquid product. Should the propellant within the liquid product become gaseous, gravity forces will cause the resultant bubbles to rise to the liquid/ gas interface and join the gaseous propellant phase. A reduction in the head space pressure, such as results where the same amount of material must occupy increasing volumes, lowers the pressure on the propellant in the liquid product. Sufiicient liquefied propellant their goes to the gas phase, and leaves the liquid product, to increase the head space pressure to a value inhibiting further vaporization. An equilibrium is established between the liquefied (dissolved) propellant in the liquid product and the gaseous propellant in the head space. Any increase in the head space volume upsets this equilibrium and requires additional propellant from the liquid product to establish a new stable relationship or equilibrium between the liquid and gas phases.

It has been explained that successive use of aerosol packages increases package head space and lowers concentration of liquefied propellant in the liquid, dispensible product. This variation in propellant levels in the product causes variations in foam quality during product use.

The present invention is premised on the addition of propellant to the increasing volume occupied by the gaseous phase propellant from a source independent of the liquid product/ liquefied propellant mixture. This mode of propellant supply accomplishes both the maintenance of pressure in the head space and the retention of adequate foaming level of liquefied propellant in the liquid product.

Referring again to FIG. 1, the body 42 of liquefied propellant is a reservoir or reserve supply of liquefied propellant which will as the container head space portion 38 increases in volume vaporize to a proportioned extent necessary for maintenance of gas/ liquid equilibrium without loss of any liquefied propellant from the liquid product. As depicted in the FIG. 1, the body 42 has vaporized and been lowered from its original charged level shown by dotted line 48 to the illustrated level at line 50. The quantity of propellant charged to the container is such that the liquefied propellant body 42 occupies from 0.1 to 10% of the container interior volume 24, with particularly satisfactory results being had with a body 42 ranging from l to 5% of the interior volume. Precise propellant body size can be calculated for a given product, propellant and container relation taking into account the use pattern and environment. In general, the amount of propellant coalesced to form body 42 will be that amount sufficient to fill the head space at pressures enabling satisfactory expulsion of liquid product solely by vaporization of the body, i.e. without loss of propellant from the product.

It will happen in use that the container l is upset or used sideways or encounters other mishaps, tending to destroy the layered interior arrangement. With reference to FIGS. 2a, b and c, the results of complete inversion of the container 16 followed by righting thereof is shown with respect to dispersion of gaseous propellant into the liquid product in FIG. 2a and with respect to dispersion of liquefied propellant into the liquid product in FIG. 2b. In FIG. 2a the gaseous propellant dispersed in the liquid product 40 as bubbles 52 is seen escaping from the liquid to the gaseous propellant 44 in head space 38. Cf. FIG. 2c. Similarly, the dispersed liquefied propellant '54 from -body 42 by ygra-vity tends to rise from the liquid product 40 in which it is dispersed but not dissolved to reform the liquefied propellant body, again as shown in FIG. 2c.

In FIG. 2b, the propellant body only is dispersed through the liquid product, resulting in a two phase liquid, which will separate by gravity to reform the separate liquefied propellant body 42 as shown in FIG. 2c.

Referring to FIG. 3, there is provided a mechanical separation in the form of an impermeable membrane or disc 56 of polyethylene, polyvinylidene chloride or the like adapted to ride vertically on dip tube 22 with movement of the level of liquid product 40 on which the disc floats. The function of the disc is to separate mechanically the propellant reservoir body 42 from the liquid product layer 40 to preclude intermixing therebetween destructive of the propellant body.

It will be apparent from the foregoing that the reservoir body is maintained independent of other propellant mate rial in the container. While this independence can be secured in a number of ways e. g. an impermeable membrane at the reservoir-liquid product interface such as a floating disc of FIG. 3 described above with many products, the mutual miscibility characteristics of liquid products and propellant are such as to enable facile separation of several phases without resort to mechanical devices.

Thus, for example, common propellants being generally hydrocarbon-based are of limited solubility in numerous liquid products which are aqueous solution of one kind or another. Advantage may be taken of the limited compatability of such system components by incorporating in a container a sufficient amount of propellant so that under prevailing temperature conditions more propellant is liquefied in the container than can be dissolved in the liquid product. The excess liquefied propellant is then coalesced to form the reservoir body above described. And this body is in phase equilibrium With gaseous propellant in the container. In this embodiment of the invention the liquefied, coalesced propellant acts as a divider between the gaseous propellant and the liquid product, in the manner of an impermanent disc or float. For ease of setting up the arrangement of layering, a propellant lighter than the liquid product is selected, otherwise special provision to provide communication between gaseous and coalesced liquid phases of the propellant must be made across or through the liquid product. It is not sufficient to have the liquefied propellant dispersed through the liquid product. i.e. an emulsion of the two materials in which the liquefied propellant is not coalesced and in phase equilibrium with the -gaseous propellant since the dispersed propellant will be then expelled with the product and have no opportunity to vaporize and replenish the head space to maintain suitable pressure there.

Among suitable propellants are those normally gaseous materials, generally nontoxic, which can be compressed to a liquid phase under pressures obtainable in a valved dispensing container of the aerosol type. Illustrative and by no means the only materials useful as propellants herein are hydrocarbons having from 1 to 4 carbon atoms halogenated versions of these hydrocarbons particularly hydrocarbons containing 1 to 2 carbon atoms and substituted with at least two halogen groups such as chloro and/or fluoro groups, and especially those containing both chloro` and fiuoro groups. Fully halogenated hydrocarbons, properly perhalocarbons generally are heavier than typical liquid products and will not be used with such products in the absence of special provision for providing an interface between the liquefied and gaseous phases of the propellant. Specific suitable propellant materials include, propane, isobutane, butane and mixtures thereof, difiuorodichloromethane and dichlorotetrafluoroethane. Propellants having heterochains acting as hydrocarbons, e.g. dialkyl ethers such a diethylether, as well as certain halogenated olefins particularly vinyl chloride can be employed in replacement of all or part of the hydrocarbon propellants described.

The liquid product may be any material normally liquid or capable of being rendered liquid by solution in an ap propriate solvent or otherwise and desirably dispensed from an aerosol package. Thus natural and synthetic fpolymeric materials such as hair setting laquer, cleaning and/ or deodorizing materials such as soaps and germacides, and foodstuffs such as artificial whipped cream may all be formulated into liquid products suited to use herein. Suitable solvents are well known and include a preferred class various hydroxylated materials both inorganic such as water specifically an organic typically `and importantly the liquid alcohols and glycols with or without addition of water in up to major amount.

The aerosol package, in common with conventional packages may include various inhibitors, colorants, perfumes, stabilizers, diluents and other additives in conventional, effective amounts for their usual purpose.

An important usage of the present invention is in the formulation of aerosol shaving soaps. These products currently enjoy more than of the shaving soap market and reduced product variation from beginning to end of use and from package to package should further increase their popularity. This invention by broadening the package tolerance, without product variation, for under an overcharging propellant and by assuring uniform foaming throughout package life will contribute importantly to further success of aerosol soap products.

EXAMPLE There was charged to a clear glass aerosol container such as depicted in FIG. l, a solution comprising the following, weight percents based on the final package.

Ingredient: Weight percent Stearic acid 6.0 2-Amino-2-methyl 1,3-propanediol 3.5 Diethanolamine-lauric acid amide 2.5 Propylene glycol 5.0

Water, deionized 77.5 Propellant (isobutane) 6.0

The propellant was a mixture of propane 15% and isobutane There can be substituted for this propellant 7% by weight of diuorodichloromethane-isobutane mixture (sp. gr. 1) for equivalent results. Additional propellant Was charged to provide a layer of liquefied propellant amounting to about 1% of the container volume.

Successive discharge of the aqueous soap solutions resulted in progressive vaporization of the liquefied propellant layer, maintaining foam density of the shave cream `at a highly desirable level for optimum wetness through first to last discharge.

Between certain of the discharges the container was inverted or shaken, then permitted to stand prior to use. Results continued satisfactory, indicating the incompatibility of the excess propellant in the shaving soap formulation and the maintainability of a coalesced liquefied propellant phase in an aerosol dispensing container.

I claim:

1. An aerosol package including a pressure-resistant container having a dispensing means and within said container a liquid product and a liquiable but normally gaseous propellant, said propellant including a gaseous phase lling the head space of said container, a liquid phase comprising a coalesced body exteriorly of said product, and a dissolved phase comprising a quantity of said propellant dissolved in said product, said gaseous and said liquid phase being in equilibrium at a desired dispensing pressure, said liquid and dissolved phases being in equilibrium to give a desired foaming when dispensed at said pressure, the quantity of said liquid phase being sufficient to rnaintain said equilibrium with said gaseous phase until substantial emptying of said container.

2. Package according to claim 1, in which the amount of liquefied propellant in the container is greater than that stably dispersible in said liquid product.

3. Package according to claim 1, in which said liquid product in contact with said liquefied propellant body is saturated with propellant.

4. Package according to claim 1. in which said liqueiied propellant body is in the form of a layer between said product and gaseous propellant.

5. Package according to claim 1, in which said liquid product comprises an hydroxylated solvent soluble material dissolved in a solvent therefor and said propellant is a low molecular weight organic compound.

6. Package according to claim 5, in which said propellant is a halogenated hydrocarbon having substituents selected from chloro and fiuoro groups.

7. Package according to claim 1, in which said body initially comprises 0.1 to 10% 0f the volume of the container.

8. Package according to claim 1, in which said dispensing means includes a valve and a dip tube extending therefrom into the container and through the liquefied propellant body to said liquid product.

9. Package according to claim 5, in which said liquid product comprises soap dissolved in water.

References Cited UNITED STATES PATENTS 2,794,579 6/ 1957 McKernan 222-399 2,849,323 8/1958 Young 222-394 2,950,846 8/1960 Clark et al. 222-399 3,099,370 7/1963 Hein 222-389 3,099,608 7/1963 Banker 222-394 X ROBERT B. REEVES, Primary Examiner H. S. LANE, Assistant Examiner U.S. C1. X.R. 222-394 

